An image-forming device for a conventional stator disclosed in Japanese unexamined patent application publication No. 2003-333513, for example, creates index data allowing a user to view a plural pieces of image data (image files) stored in an external storage as thumbnail images. If the image file contains preview image data independently of actual image data, the image-forming device creates the index data using the preview image.
In the above invention, expanding the image file is required for determining whether or not each piece of image data contains preview image data, for all image file stored in the external storage. Accordingly, the amount of time required for creating index data is difficult to reduce.